Lamp cap for tubular electric lamps



Feb. 2, 1954 (2. H. J. ANDERSON ET AL 2 68277 LAMP CAP FOR TUBULAR ELECTRIC LAMPS Filed Aug. 2, 1950 2 Sheets-Sheet 1 INVENTORS C.H.J. ANDERSON J.H.F. VAN WERD AGENT Patented Fel). 2,1954

LAMP CAP FOR TUBULAR ELECTRIC LA1IPS Charles Henri Joseph Anderson and Johannes Hendricus Franciscus van Werd, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn., as

trustee Application August 2, 1950, Serial No. 177,263

Claims priority, application Netherlands August 11, 1949 2 Claims. (Cl. 339-52) The nvention relates to lamp caps for tubular electric lamps, more particularly for low-pressure mercury-vapour discharge tubes, the lamp caps comprising one or more contacts housed in an insulating body.

It has been suggested te construct such a cap so as to enable it to be inserted in a. holder in a particular position transverse to the axis of the lamp and. to be locked therein by rotation, it being suggested in addition to provide on the outside of the insulating body an extension adapted to engage a grVe in the holder when rotated. This construction readily gives rise te difliculty, if the lamp is placed in a slanting position in the holder, since in this position a comparatively large deviation of the extension occurs in an axial direction, so that it cannot be turned te engage the groeve or becomes jammed therein.

This difiicul-ty is particularly prevalent with these lamp caps in which the contact or contacts are fitted in an insulating body, since in the conventional constructions th diameter of this body is comparatvely large. If the lamp has a contact in the form of a, single axially protruding pin, this problem does not arise, but such contacts are objectionable in a number of cases, particularly because they are easily accessible when they are alive.

According to the invention the lamp cap has an axially directed extension, in which one or more contacts are housea;in an insulated manner, the extension having a smaller diameter than the cap and having a slot in its periphery. This slot may be provided without interruption around the entire extension, but as an alterna tive it may be interrupted at one or more points.

With this construction the lamp holder may be designed so that the slot acts as a lockng means. Since the extension has a comparatively small diameter, the lamp may b introduced into the holder in a comparatively slanting position, without jamming occurring.

Obviously, the extension shollld not be made so thin that its rigidity is alected. According to a preferred embodiment of the invention, the diameter of the extension ranges between /3 and of the diameter of the cap. The diameter of the extension is to be understood te mean the maan value of the diameters in the slot and at the side thereof. The diameter of the cap is to be measured at the part of the cap adjoning the glass of the lamp.

The extension may be provided with lugs by whichit is enabled to control a rotatable member provided in the holder. Rotaton or the member permits the circuit of the lamp te be controlled so that the holder contact te be connected to the lamp cannot become alive, unless the lamp is inserted in the holder.

Such caps are to be provided one at each end of the lamp. With such lamps having a cap at each end, it is desirable that a tolerance in the position of the aXis of the holder relative to the axis of the lamp should be possible, because in this case the position of the lamp axis is determined by the line connecting the bolders and deviations from this position should also be possible durng insertion of the lamp, in contradistnction to the conditions obtaining with other caps, particularly with the bayonet cap, of which only one is provided on each lamp, the lamp being free to occupy the position determined by the holder.

In order that the invertion may be readily carried into effect, an example will now be described in detail with reference to thaccompanying drawings of the cap and associated lamp holder, in which:

Fig. 1 is a view of that side of the holder which is remote from the side on which the lamp is introduced and which will be termed the rear side, the rear wall of the holder and the rotatable member being removed;

Fig. 2 is a sectional view taken en the line IIII of Fig. 1;

Fig. 3 is a sectional view taken on the line IIIIII of Figs. 1 and 2;

Fig. 4 is a view of the rear side of the movable member and.

Figs. 5 and 6 are respectively a sectional view and an end view of the lamp cap -to be used with this holder.

Fig. '7 is a side view of the same lamp cap.

Fig. 8 is a side view of the holder as seen from a direction, opposite to that from which it is seer1 in Fig. 1.

The holder comprises a socket I, which is made of insulating material, for example mouldea material. The top of the socket is provided with an aperture 2, through which one end of the lamp cap can be introduced (from the top, as viewed in Figs. 1, 2 and 8), the lamp being moved transversely with respect to ts longitudinal axis. Arranged around the aperture 2, en the bottom 3 of the socket, is an approximately horse-shoeshaped edge 4, the opening 5 of which is turned upwards. This edge l (shown for the greater part in braken lines in Fig. 2) constitutes a seat for the movable memberli, which is -urged=against 2,ees,277

this seat by a helical spring 1. On its rear side the spring 1 bears on a plate 8, which is preferab1y also made of insulating material and which constitutes the rear wai1 of the bolder. At its upper side it is held under a hook-shaped part 3 of the socket I and at its 1ower side by a fianged rivet HI.

At the bottom end of the soclret l an elevation II defines a recessed seat l2 for the bottom end of the stationary contact l. This contact is a curved spring, the top end is of which engages the periphery of the movable meznloer 6 and the bottom end of which has a bent hook-like part 15, which fits in the seat 12. This part is perforated to receive a screw l carrying a nut i1, the latter two being housed between the socket i the rear wall 8. The screw can be tightened through an aperture l8 in the socket so as to enable a conductor to be gripped between the nut I1 and the hook-like part 15.

The movable member 5 (Figs. 2 and 4) is constituted by a disc of insulating molded materi 1, the front side of which is conically bevelled at the edge at !9 so that under the acton of the spring 1 it is urged into the centre of the seat of the edge 4. I-Iowever, there is no objection to its occupying tilted positions, if such is required by the position of the lamp relative to the helder. The rear side of the member 5 defines a cavity 20, adapted to receive the spring 1. The front wall of this cavity is provided with an elongated aperture 2i, through which two crescent-shaped contact plates 22, which together constitute ons contact, are introduced from the rear side. Bach of these plates is integral with a strip 23, which extends across the rear sicle of the member 55 and forms a contact area 24 at the periphery thereof. The member 6 is provided at its periphery with four grooves '25, in two of which are located the strips 23. The plates 22 are retained in the member by the spring 1 with the intermediary of an insulating plate 26.

The lamp cap (sec Figs. 5-7) for use with these lamp bolders is constituted by a cap 21 to be anplied to the tubular lamp, the bottom of which has a circular aperture 28 having two elongated extensions '29. In Fig. 6 this aperture is shown in broken lines.

A body 311 of insulating material is introduced by means of two lugs 31 through these extenthis flanged rivet, the width of the aperture 2a being such that adequate insulation of the flanged rivet 33 from the cap 21 is saeguarded.

The insulating body 3EI comprises in addition two projecting portions 35, which extend beyond the cap '21 and which are spaced by the transverse slot 31 (a sde wall of which is shown in Fig. 5). A peripheral groeve 38 surrounds the projecting parts 35 adjoining the cap. These projecting portions 35 constitute the lugs which are adapted to cause rotation of the memoer 6 provided in the holder. The bottom of this groove has a circular perphery with two flattened parts as shown by the broken lines in Fig. 6. The dstance A between these fiattened parts is slghtly smaller than the width B of the aperture 5 of the bolder as shown by Fig. 6 and Fa 1 respectv y The operation of this holder will be described for one end of the lamp. A simiiar helder is 4 provided at the other end. Different features of the bolder are urther described and claimed in one of the following copending applications: Serial Nos. 177,261; 177,262; 177,264; a11 filed on August 2, 1959.

The bolder is mounted while the member 6 occupies the position shown in Fig. 2. The contacts 22 cannot yet be alive, since the end l4 of the stationary contact 13 does not engage one of the strips 23 (Fig. 4).

One lamp end is introduced into the helder from above and turned in a marmer such that the body 3G passes through the aperture 5, the slit 31 located between the lugs or eyelets being directed so that the contact plates 22 move inside and establish a contact with the conductor 35 by way of the flanged rvet 33. If the lamp is then turned through 99 about the lamp axis, the 1ugs 3b engage the contact plates 22, cause the member '3 to rotate and one of the strips 23 is thus brought into engagement with the 'end U! of the stationary contact !3. This contact can now be alive. At the same time removal of the lamp is prevented while t is in the rotated position. In this position, the contact plates 22 are engaged between the projecting lamp cap parts, and the enlarged portion of the floor of groove 33 can not pass through the aperture 5. A shift of the lamp in the axial direction is impossible, since the projecting portions 36 are enlarged beyond groov-e 353 and engage the wall of the socket 1 behind the face of the aperture 2.

Safety trom electric shock is ensured with this holder, since it is not possibie to remove the lamp from the helder without the contacts 22 oeing first switched off. It is possible to introduce oniy one of the lamp ends into a helder and then to turn the lamp. The contact on the cap at the other end of the lamp may now be alive by way of the impedance of the lamp, but the slt 31 is narrow and deep enough to prevent this contact being touched accidentally.

It may be seen most clearly from Fig. 5 that, if a lamp provided with a cap having locl;ing extensions is introduced into the bolder crookedly, diiculties may arise if the extensions have the same diameter as the lamp. This slanting position would cause the extensions to be subjected to an axial displacing force, With the result that either they could no longer be caused to occupy their position in the helder or they might lead te breakage of the holder.

The cap described above in which this dificulty is avoided, is intended for use particularly with low-piessure mercury-vapour discharge tubes, so-called fluorescent lamps, but it may also be used with tubular incandescent lamps whch are provided with a contact at each end.

What we claim is:

1. A lamp cap for a. tubular electric lamp having an elongated bulb portion, comprisng an axially-extending locking hub having a smaller diameter than the diameter of sad cap, said locking hub having a transversely extending fiange portion at the outer end thereof adapted to engage locking portons of a lampholder to prevent direct withdrawal of the bulb when its attached cap is inserted in the lampholder and the lamp then rotated, said hub having a slot extending transversely across the entire hub at its outer end for receiving a contact plate of the lampholder, and an electrical contact mamber extending through the hub and terminating Wh.-' ing the bottom of the slot for making electrical 2,668,277 5 6 contact with the contact plate when the cap is References Cited in the fl1e of this patent inserted in the lampholder and thereby protect- UNITED STATES PATENTS ng the contact member from external engagement b objects too large to fit wthn the slot. Numbe1' Name Date 2. A amp cap for a tubular electric lamp hav- 5 2014843 Hlrmann sept 1935 ng an elongated bu1b portion as claimed in claim 2288376 Tuppen Tune 1942 1 in which the lockng hub has a diameter from FOREIGN P N S about to the diameter of the cap. Number Country t 10 533,132 Great Brtan Feb. 6, 1941 CHARLES HENRI JOSEPH ANDERSON. 536,275 Great Brtain May 8, 1941 JOHANNES HENDRICUS 583,724 Great Brtan D60. 30, 1947 FRANCISCS VAN WERD. 610,984 Great Brtan O0t. 22, 1948 

